Exploring the Non-Gaussianity of the Cosmic Infrared Background and Its Weak Gravitational Lensing

TL;DR

This paper investigates how gravitational lensing affects the non-Gaussian statistical properties of the Cosmic Infrared Background (CIB), revealing significant modifications in higher-order correlations and proposing methods for lensing estimation.

Contribution

It introduces a novel analysis of lensing effects on CIB non-Gaussianity using needlet-like filters and PDFs, expanding understanding beyond power spectra.

Findings

Lensing alters 3-point and 4-point functions by tens of percent at large scales.

Power spectrum changes are less than two percent due to lensing.

Relative entropy of PDFs can be used to estimate lensing effects.

Abstract

Gravitational lensing deflects the paths of photons, altering the statistics of cosmic backgrounds and distorting their information content. We take the Cosmic Infrared Background (CIB), which provides plentiful information about galaxy formation and evolution, as an example to probe the effect of lensing on non-Gaussian statistics. Using the Websky simulations, we first quantify the non-Gaussianity of the CIB, revealing additional detail on top of its well-measured power spectrum. To achieve this, we use needlet-like multipole-band-filters to calculate the variance and higher-point correlations. Using our simulations, we show the 2-point, 3-point and 4-point spectra, and compare our calculated power spectra and bispectra to Planck values. We then lens the CIB, shell-by-shell with corresponding convergence maps, to capture the broad redshift extent of both the CIB and its lensing convergence. The lensing of the CIB changes the 3-point and 4-point functions by a few tens of percent at large scales, unlike with the power spectrum, which changes by less than two percent. We expand our analyses to encompass the full intensity probability distribution functions (PDFs) involving all n-point correlations as a function of scale. In particular, we use the relative entropy between lensed and unlensed PDFs to create a spectrum of templates that can allow estimation of lensing. The underlying CIB model is missing the important role of star-bursting, which we test by adding a stochastic log-normal term to the intensity distributions. The novel aspects of our filtering and lensing pipeline should prove useful for any radiant background, including line intensity maps.